In questa situazione con due UpdatePanel e due timer, ognuno all'interno del suo panel,
perchè mi si aggiornano tutte le textarea anche se il timer in funzione sta dentro all'updatepanel2??? 
grazie
codice:
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Timer ID="Timer1" runat="server" Enabled="False" Interval="1"></asp:Timer>
<!-- <asp:TextBox ID="txtConsolle" runat="server" BackColor="Black" BorderStyle="Inset" Font-Names="Consolas" ForeColor="Lime" Height="263px" TextMode="MultiLine" Width="469px" ReadOnly="True" Font-Size="Small"></asp:TextBox> -->
<br />
<textarea runat="server" id="TextArea1" aria-multiline="False" aria-readonly="True" style="font-family: Consolas; font-size: 10px; color: #00FF00; background-color: #000000; height: 246px; width: 469px" readonly="readonly"></textarea>
<%--<script>
var textarea = document.getElementById('TextArea1');
textarea.scrollTop = textarea.scrollHeight;
</script>--%>
<br />
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="Timer1" EventName="Tick" />
</Triggers>
</asp:UpdatePanel>
<asp:TextBox ID="txtcomandi" runat="server" BackColor="Black" BorderColor="silver" BorderStyle="Inset" Font-Names="Consolas" ForeColor="Lime" Style="margin-top: 0px" TextMode="SingleLine" Width="412px" Height="16px" AutoCompleteType="Disabled" Font-Size="10px"></asp:TextBox>
<asp:ImageButton ID="EnterBtn" runat="server" BackColor="#999999" Height="20px" ImageUrl="~/image/Enter Key-64.png" ToolTip="Enter" Width="50px" />
</td>
<td>
<table id="tablechat" runat="server" style=" align-content: center" >
<tr>
<td >
<asp:UpdatePanel ID="UpdatePanel2" runat="server">
<ContentTemplate>
<asp:Timer ID="Timer2" runat="server" Interval="3000"></asp:Timer>
<textarea runat="server" id="TextArea2" style="font-family: Consolas; font-size: 10px; color: #00FF00; background-color: #000000; height: 257px; width: 235px" readonly="readonly" name="S1" aria-multiline="False" ></textarea>
<%-- <script>
var textarea = document.getElementById('TextArea2');
textarea.scrollTop = textarea.scrollHeight;
</script>--%>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="Timer2" EventName="Tick" />
</Triggers>
</asp:UpdatePanel>
</td>
</tr>
<tr>
<td style="text-align :left" class="auto-style13">
<asp:TextBox ID="TxtMessage" runat="server" AutoCompleteType="Disabled" BackColor="Black" BorderStyle="None" ForeColor="Lime" Wrap="False" Width="220px" ></asp:TextBox>
<asp:Button ID="btninviochat" runat="server" BorderStyle="None" Text="Send" style="text-align: center" Width="42px" />
</td>
</tr>
</table>